The present invention relates to a method for the manufacture of diodes which have light emitting and detecting properties. More specifically these diodes are able to emit light with a clearly defined wavelength when an adequate electrical voltage is applied thereto or can form the source of a current when subject to the action of light radiation. Certain of the diodes manufactured according to this method can have both of these properties at the same time.
More specifically the invention relates to diodes having these two types of properties and which are manufactured from a composite semiconductor material.
Light emitting diodes are already known which are constructed by ion implantation in a semiconductor substrate of zinc telluride ZnTe. The operation of such diodes has been described by Pfister and Marine in Acta Electronica 1976, page 166.
With the aim of improving the properties of such diodes and in particular to increase their emission and reception efficiencies and to give them the capacity of operating in either emission or reception as required, an improved method for the manufacture of diodes by ion implantation has been developed and is covered by French Patent Application EN 78 08522 of Mar. 23, 1978 in the name of the Commissariat a l'Energie Atomique. The improved method of this French application is essentially characterised by producing a compensated layer having a high resistivity in the ZnTe plate surface prior to ion implantation. This layer is more particularly obtained by thermal diffusion of the constituent atoms of a conductor deposit covering the semiconductor plate.
However, said diodes produced by ion implantation in zinc telluride have a number of shortcomings:
The emission wavelength is limited and, as the band gap of ZnTe is 2.3 eV, it is not possible to obtain a higher energy emission, e.g. a blue luminescence.
The spectral reception region is limited to the band of 2.3 to 2.82 eV, also fixed by the band gap of ZnTe.
In particular, in emission, these diodes have a large number of black lines indicating the presence of dislocations in the starting material, said dislocation lines being non-radiative recombination zones which enlarge with time. Furthermore, at the end of a few hours operation the non-radiative zones cover the entire surface and finish up by making the diode very inefficient in emission.